1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting a liquid, and more specifically relates to a liquid ejection head having a ejection orifice row including a plurality of ejection orifices.
2. Description of the Related Art
An example of a liquid ejection head that is to be mounted in a main body of a liquid ejection apparatus is disclosed in Japanese Patent Application Laid-Open No. 2010-18027. In the liquid ejection head disclosed in Japanese Patent Application Laid-Open No. 2010-18027, an element substrate that includes a ejection orifice row constituted by a plurality of ejection orifices is supported by a support member. A flow path is formed inside the support member, and the flow path communicates with a supply port formed in the element substrate. A liquid is supplied to the ejection orifices via the flow path of the support member and the supply port of the element substrate.
In this connection, air bubbles in the flow path of the support member sometimes constitute a problem in the liquid ejection head. The air bubbles are caused by a gas that flows into a liquid receiving portion together with a liquid when filling the liquid into the liquid receiving portion, a gas that is dissolved in the liquid, or air that permeates a constituent member of the liquid ejection head. If air bubbles build up inside the flow path of the support member, the air bubbles hinder the flow of the liquid, whereby an ejection failure occurs.
As a method for suppressing the occurrence of the aforementioned kind of ejection failure, a method has been proposed that periodically sucks liquid from ejection orifices to eject air bubbles from the liquid ejection head together with the liquid. Further, in Japanese Patent Application Laid-Open No. 2010-18027, a configuration is disclosed in which a flow path of a support member is formed in a shape that is suitable for ejecting liquid and air bubbles when sucking the liquid. More specifically, the flow path of the support member is formed in a shape in which a cross section that intersects with a flow direction of a liquid increases from an upstream side to a downstream side with respect to a direction in which the liquid is supplied.
In recent years, there is a demand to lengthen a ejection orifice row for the purpose of ejecting liquid over a wider range. However, a new problem with respect to a liquid ejection head that arises accompanying lengthening of an ejection orifice row has become evident. The new problem will now be described using FIG. 11.
FIG. 11 is a cross-sectional view that schematically illustrates the inner structure of a liquid ejection head disclosed in Japanese Patent Application Laid-Open No. 2010-18027. In a liquid ejection head 1 illustrated in FIG. 11, a plurality of ejection orifices 2 is formed in an element substrate 3. The ejection orifices are aligned in a predetermined direction to form an ejection orifice row 4. In the present specification, the predetermined direction is also referred to as “arrangement direction X”.
A supply port 5 is formed in the element substrate 3, and a flow path 7 is formed in a support member 6. Note that, in the present specification, a direction in which liquid flows in the flow path 7 is also referred to as “flow direction Y”. The liquid is supplied from outside of the support member 6 to the ejection orifices 2 via the flow path 7 and the supply port 5. A cross section of the flow path 7 that intersects with the flow direction Y increases progressively in the flow direction Y.
If the ejection orifice row 4 has been lengthened in the arrangement direction X, the supply port 5 must also be lengthened in the arrangement direction X. Accompanying lengthening of the supply port 5, it is desirable to enlarge, in the arrangement direction X, a connection port of the flow path 7 that is connected to the supply port 5 (hereunder, the connection port in question is referred to as “outlet 8”). If the outlet 8 is enlarged in the arrangement direction X without changing the size of a connection port of the flow path 7 that is on the opposite side to the outlet 8 (hereunder, the connection port in question is referred to as “inlet 9”), the length of a wall surface 10 of the flow path 7 with respect to the flow direction Y will increase, and furthermore an angle θ with respect to the flow direction Y will also increase.
The present inventors discovered that, as the length of the wall surface 10 of the flow path 7 increases, the air bubbles 11 are liable to stagnate more at ends in the arrangement direction X of the outlet 8.
Thus, it became clear that in the liquid ejection head disclosed in Japanese Patent Application Laid-Open No. 2010-18027 there is the problem that an ejection failure that is caused by the air bubbles 11 is liable to occur in a case where the ejection orifice row 4 is lengthened and the angle θ is enlarged.